Method of and apparatus for making photophonographic records



Oct. 13, 1931. F. E HRENHAFT 1,826,754

"ETHOD OF AND APPARATUS FOR MAKING PHOTQPHONOGRAPHIC RECORDS Fiied Oct. 1, 192a V]//////// AV/ /.A'

charge Patented a. 1a, 1931 PAT ENT orrlcs I I 0] mLm-monrmmm, GERMANY mon 01" AIPLRLTUS FOR MAKING PHO'IOPHONOGRLPEIC RECORDS Application fled October 1, 1988, Serial Ho.

This invention relates to a method of andapparatus for makin photo-shonogra hic records by means of electrical evioes w 0b are able to produce light discharges acting 5 u n a light-sensitive layer such as a film w 'ch forms the carrier of the photo-phonographic record.

It is well lmown-to use sources of li ht which are controlled by sound-waves in 0 er to make hoto-phonographic records. Principally, t ere are two possibilities of controlling light discharges forthis purpose, viz: in the first lace a constant source of light may be mo ulated as to its action upon the sensitive layer {or the photo-phonographic record, or in the second place, the emission of light itself-from the source may be controlled in accordance with the sound-waves. Accordin to my invention the latter mode of contro ling l ht dischar es is employed.

In' order to so ve the pro lem underl g my present invention, various schemes ave been proposed. .All propositions so far made, however, are connected with certain disadvantages which are entirely avoided by my present invention.v The twoosegrmcipal so utions which have been prop for the ,present pu'rpose consist, firstly, in usin socalled glow discharges as pro ose by 3o Gehrke, and secondl ,musin arc- 'schar es according to theear y work 0 Ruhmer. ccor to my invention, now, a special form of disc arge is used which is a transitional -form of a glow discharge and an arc-dis- The discharge whichv is used according to my invention, although being a transitional form of discharge, may wellbe armed a glow discharge, though not of Geisslers type.

When using glow discharges for producing photo-phon phic records, the disadvantage arises, the quantities of light which are at disposal are nerally not sum- ,cie'nt in order to properly lacken the lightj I "sensitive layer in order toproduee the photo- 809,674, and in Germany October 1, 1927.

phonographic record. This is due to the short time of exposure necessary for the present purpose. The said disadvantage consists therein that a glow dischar e by reason of the cold cathode which is a c aracteristic feature of this kind of discharge does not generate an appreciable discharge of electrons due to thermionic action. On the other hand the glow discharge is connected with the advantage of being an independent electrical discharge.

In the arc-discharge which had been pro posed for the present purpose, there are like wise space-charges present intermediate the electrodes; in general the arc-discharge is 50 characterized by the fact that the cathode is heated up to the point of evaporation. It is known since along time that for the present. purpose only a limited number of specific arc-producing devices come into consideration. More articularly, only arc-producing devices may used for the present purpose in which the evaporated metal again deposits upon the cathode, thus giving off the asparticles which had previously beenabsor ed by the metal particles. It may be noted that only in this'way it will be possible to practically maintain constancy of the contents of gas as well as of the discharge.

However, even this specific kind of arc-dis- 7 charges'which may mostadvantageously be nerated by means of a mercury vapor lamp,

oes not permit to maintain constancy of the arc to the extent required for the purpose of producing photo-phonographic records. Besides, in case of arc-dischargesthere will always be disturbing noises which have a disagreeable eflect upon the faithful and enjoyable reproduction of the photo-phonographic record. On the other hand, the arc-discharge has without doubt the advantage that it will produce a greater brilliancy of the light and in consequence hereof greater cpntrasts'in the photo-phonographic records. Also, when using an arc-discharge :it will be possible to shorten .the time of ex posure, or what is the same to increase the velocity of motion of the film-band or other from a discharge of this character as regards its mode of operation. This difference of the form of discharge which I use according to my invention is due to certain characteristic properties of the cathode, which properties do no more characterize the discharge as a glow discharge.

In order to produce photo-phonographic records I naturally use an electrically controlled luminescent gas-discharge in which space-charges are ,present intermediate the electrodes, and which. may: be generated by means of electrodes consisting of any desired materials.

The impressed voltage will at first produce a glow discharge; On account of the heat imparted to'the electrodes, especially to the cathode, during passage of current there will be produced an increased thermionic effect. The electron-emitting properties which are inherent to manysubstances when being even moderately heated, have heretofore never been considered for the present purpose, in spite of the special effect which is roduced by these properties It may be no thatthe electron emission produced by thermionic I action will increase the discharge by the eflect of shock-ionization in sncha manner, that the discharge will assume a character which can no more be defined by any of the heretofore .known definitions. Y

The glow discharge which I use accordin to my present invention,-now forms part the c ass of independent discharges,-while the arc-discharge as known is not an independent discharge. According to my invention therefore, a'modified or transitional form of discharge is brought about by a glow discharge, said modified or transitional discharge being characterized by an increased emission of'hght.

In the accompanymg drawing I have shown in a diagrammatlcal wayan example of the devices and their electrical connections which serve for carrying my invention into effect.

From the. microphone circuit 1 the electrical current impulses are transmitted by way of a transformer 2 to the am lifying tube3', whence said impulses are furt er transmitted By way of another transformerito the lamp circuit. The. lamp'5 which serves for Y roducing-thephote-phonographich recor -is supplied withcurrent from a battery 6, avoltage of about 500 to 700 volts being impressed on said lamp, the operatingcurrent amounting ordinarily to from 80-35 milliamperes. The lamp 5 is mounted in a lampsocket 7. Within the bulb of the lamp 5 there is provided an anode 8 which, for instance, may consist of a tungsten point and a cathode 9, for instance, in the form of a small cylinder. The film-band 11 is rolled off from its carrier 12 and moved past the lamp 5, a shield 13 with a slot 14 therein bein interposed between the lamp and the film-land,

By'means of a regulating resistance of high resistance value the passage of current through' the lamp 5 may be regulated to a value about from to milli-amperes, at which value of current the form of discharge will be stablized and an unstable arc prevented.

The lamp 5 is preferably filled with nitrogen having a pressure of about 30 mm. mercury column. However, also other gases may be used in the lamp at pressures differing from the aforementioned pressure. Although the nitrogen will become luminescent during operation of the lamp and create the impression of a glow discharge, an arc-discharge will be present which besides the luminescence of the nitrogen is characterized by evaporation. of the cathode. The electrical discharge taking place in the lamp is a typical transitional form of dischar e which is intermediate a glow discharge an an arcdisizharge, as had, for instance been described by Compton, Seeliger and others, The conditions which are characteristic for the roduction of this transitional form of arge consist in general in the use of a regulatmg'resistance of a high resistance va ue' in connection with a current source of high electromotive force. In this case the current strength is artificially ke t within certain limits above a stable glow 'scharge. The incandescence of the cathode is essentlal for the practical production of the transitional form of discharge which I use accord [ing to my invention and is not a mere inci tal feature tifsaid transitional discharge. 1 o v- 1. The method of making photo-phonographic records by means of a luminescent gas-discharge "controlled by sound-waves, which method consists in'transforming said luminescent gas-discharge intoa transitional form of discharge'intermediate a glow and arc-dischargei 2. The method of making photo-phonographiii'records by means of a light-source in the form of a luminescent gas-discharge conerative condition thereof, so asito transform said discharge into a transitional form oftrolled by -sound-waves, which method con- Sists in causing; an increased thermionic effect to take place in said discharge in opassent-1 charge intermediate a glow and arc-dischar 3. gl he method of producin photo-phonoa bio records by means 0 a luminescent isc arge controlled by sound-waves, which method consists in sup lying operating current controlled b said sound-waves to said luminescent disc arge, and regulating the value of said operating current to produce an increased thermo-ionization of said discharge so as to transform the latter during operation into a transitional form of glow and arc-discharge.

In testimony whereof I afix my signature.

FRANZ EHRENHAFT. 

